A white light-emitting unit configured to include a GaN (gallium nitride) semiconductor light-emitting device (hereinafter, “semiconductor light-emitting device” also will be referred to as “LED”) coupled to a wavelength conversion material phosphor has attracted interest as a light source of image display devices and lighting devices for its low power consumption and long life. A representative example of such a light-emitting unit is a white light-emitting unit that uses an InGaN blue LED in combination with a Ce-activated yttrium-aluminum-garnet yellow phosphor.
Such white light-emitting units have potential use in novel applications such as in display backlights, and there has been research and development of phosphors for use with semiconductor light-emitting devices.
For example, Patent Literature 1 discloses an oxide phosphor activated with Mn4+. Patent Literatures 2 to 5 disclose Mn4+-activated fluorine-containing phosphors, and light-emitting units in which these phosphors are coupled to a semiconductor light-emitting device. The fluorine-containing phosphors exemplified in Patent Literatures 2 to 5 basically contain monovalent alkali metal ions, and trivalent, tetravalent, or pentavalent ions as the coordination center metal ions of fluoride ions.